The invention relates to apparatus for separating dirt or dust from an airflow particularly, but not exclusively, to such apparatus for use in a vacuum cleaner.
Vacuum cleaners which make use of cyclonic action in order to separate dirt and dust particles from an airflow are known. Essentially, the airflow is introduced to a cylindrical or frusto-conical surface in a tangential manner so that the airflow is caused to move in a spiral or helical motion down the cylindrical or frusto-conical surface. Centrifugal forces force the dirt and dust particles radially outwardly until they come into contact with the stationary wall of the cyclone. The dirt and dust particles are then separated from the airflow and collect in a chamber. It has previously been proposed that fins, baffles or ribs be provided on the outer wall of the chamber or on the surface in order to encourage the dirt and dust separated from the airflow to settle in the container. The fins or baffles also discourage re-entrainment of separated dirt and dust, particularly when the vacuum cleaner is switched on without the collecting chamber first having been emptied. Arrangements of this type are illustrated and described in GB 2 298 598 A, U.S. Pat. No. 2,171,248 and DE 754339.
In all of the prior art arrangements, the fins, baffles or ribs intended to encourage settling of the dirt and dust and to discourage re-entrainment have been located on the outer wall of the separating apparatus. This is a natural location since the majority of the dirt and dust remaining entrained within the airflow or settled in the chamber will be located close to the outer wall. However, the arrangement of the fins or baffles on the outer wall causes some difficulties during the manufacture or assembly of vacuum cleaners of this type, particularly when components are desirably introduced to the interior of the collecting chamber and are of a similar diameter to the chamber. The projection of the fins or baffles inwardly from the outer wall makes it difficult or impossible to achieve the desired construction.
It is an object of the present invention to provide dirt and dust separating apparatus of the type described above but without the constructional disadvantages of existing arrangements. It is a further object of the present invention to provide dirt and dust separating apparatus which is easy and economical to manufacture and which has a separation efficiency equal to or better than existing arrangements. It is a still further object of the present invention to provide dirt and dust separating apparatus in which re-entrainment of dirt and dust previously separated from the airflow is discouraged.
The invention provides a cyclonic separator for separating dirt or dust from an airflow having an outer wall forming an air-rotational surface, an inner wall, a collecting area located between the outer wall and the inner wall for collecting dirt or dust separated from the airflow, an airflow inlet for introducing the airflow substantially tangentially to the outer wall, an airflow outlet for removing air from the separator, the airflow inlet and the airflow outlet being spaced apart from the collecting area, and at least one fin or baffle positioned within the separator, characterised in that the or each fin or baffle is located at least partly in the collecting area on the inner wall of the separator and projects outwardly therefrom.
Further and advantageous features are set out in the subsidiary claims.
It has been found that the removal of the fins or baffles from the outer wall to the inner wall of the collecting area of the cyclonic separator does not reduce the separation efficiency of the separator and furthermore discourages re-entrainment at least as much as the prior art arrangements discussed above. This is surprising because, given the centrifugal forces acting on the dirt and dust particles within the separator, it would be expected that fins or baffles arranged on the outer wall would have a more significant effect. However, moving the fins or baffles to the internal wall then allows a component having a diameter similar to that of the outer wall to be introduced into the container without any difficulty. The fins or baffles can be molded integrally with the inner wall or, alternatively, can be affixed thereto during construction.